For a semiconductor device, when a joining member such as an insulating member (an insulating substrate) is to be joined or bonded by brazing to a member to be joined (a joined member) such as a lid of a cooler, for example, a brazing material placed between the joining member and the joined member is heated to be melted. At that time, if a clearance or gap between the joining member and the joined member is uniform, the melted brazing material is wetted and spread with no regularity. When the brazing material is cooled and solidified to form a joining layer, a peripheral portion of the joining member is apt to become cold first, causing the brazing material to begin solidifying from an outer peripheral edge.
Thus, air existing in the brazing material is kept in the joining layer. This may leave voids (air layers) with unspecified width or area inside the joining layer. In case such voids are left, it is impossible to stably transfer and release the heat generated in an electronic component such as a semiconductor element to a cooler. Thus, a cooling performance of the cooler could not sufficiently be brought out on the electronic component.
Patent document 1 discloses a technique of releasing such air. To be concrete, a pair of electrodes to which an electronic component is to be soldered are formed with guide passages for air release. These guide passages open in a clearance located under the electronic component and in the outside of the electronic component. With this configuration, the air that occurs in the clearance under the electronic component when resin is supplied to form an insulating layer is released through open ends located in the outside of the electronic component via the guide passages.